/*
 * Copyright (c) 2013-2013, KNOPFLERFISH project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials
 *   provided with the distribution.
 *
 * - Neither the name of the KNOPFLERFISH project nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.knopflerfish.util;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;


/**
 * Misc static timer utility methods.
 */
public class Timer {

  static private Method nanoTimeMethod;

  static {
    AccessController.doPrivileged(new PrivilegedAction<Object>() {
      @Override
      public Object run() {
        nanoTimeMethod = getMethod(System.class, "nanoTime", new Class[] { });
        return null;
      }
    });
  }

  /**
   * Get method from class
   */
  public static Method getMethod(Class<?> c, String name, Class<?> [] args) {
    Method m = null;
    while (true) {
      try {
        m = c.getDeclaredMethod(name, args);
        break;
      } catch (NoSuchMethodException e) {
        c = c.getSuperclass();
        if (c == null) {
          return null;
        }
      }
    }
    return m;
  }

  /**
   * Use System.nanoTime() if available, otherwise revert to
   * System.currentTimeMillis(). Return time in milliseconds
   * that can be used for time measurements.
   */
  public static long timeMillis() {
    if (nanoTimeMethod != null) {
      try  {
        Object res = nanoTimeMethod.invoke(null, new Object[] { });
        if (res != null) {
          return ((Long)res).longValue() / 1000000L;
        }
      } catch (IllegalAccessException _ignore) {
      } catch (InvocationTargetException _ignore) { }
    }
    return System.currentTimeMillis();
  }

}
